|Publication number||US8101927 B2|
|Application number||US 12/775,728|
|Publication date||Jan 24, 2012|
|Filing date||May 7, 2010|
|Priority date||Jun 8, 2009|
|Also published as||US20100308236, WO2010144273A2, WO2010144273A3|
|Publication number||12775728, 775728, US 8101927 B2, US 8101927B2, US-B2-8101927, US8101927 B2, US8101927B2|
|Inventors||Charles T. Carlson, William T. Weaver|
|Original Assignee||Varian Semiconductor Equipment Associates, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (13), Referenced by (3), Classifications (18), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of provisional patent application No. 61/185,028, filed Jun. 8, 2009 which is incorporated herein by reference.
This disclosure relates to a masking apparatus and, more particularly to a masking apparatus for an ion implanter.
An ion implanter generates and directs ions towards a target for treatment. An ion implanter may include known beam line ion implanters that generate a well defined ion beam. A beam line ion implanter includes an ion source and an is extraction electrode assembly to extract a well defined ion beam from the ion source. One or more beamline components known in the art may control and modify the ion beam to obtain an ion beam with desired characteristics which is directed towards a surface of the target. The ion beam may be distributed across a surface of the target by ion beam movement, target movement, or a combination of the two. An ion implanter may also include known plasma doping ion implanters that generate plasma in a process chamber. Ions from the plasma are attracted towards a surface of a target during certain time intervals. The target is also positioned in the process chamber of the plasma doping ion implanter. For either type of ion implanter, the target may include, but not be limited to, a semiconductor substrate, a solar cell, a polymer substrate, and a flat panel.
An ion implanter may also be equipped with a mask to provide for selected treatment of the target. A conventional mask has one or more apertures and is sized relative to the target to provide a selected treatment over an entirety of the target. Hence, an application that requires a masked and non-masked ion treatment requires one treatment with the entirety of the target masked and another treatment with the entirety of the target un-masked. One drawback with a conventional ion implanter and mask is the time necessary to move the mask away from the target in between the masked and non-masked ion treatments. This additional time negatively impacts throughput performance. Another drawback is alignment of the mask with the target. Most masking applications require precise alignment of the mask to the target. Yet another drawback is the difficulty in retrofitting an existing ion implanter with such a full sized mask including an associated alignment system to align the mask with the target.
Accordingly, there is a need for an improved masking apparatus, ion implanter, and method that overcomes the above-described inadequacies and shortcomings.
According to a first aspect of the disclosure a masking apparatus is provided. The masking apparatus includes a mask positioned upstream of a target, the mask is sized relative to the target to cause a first half of the target to be treated with a selective treatment of ions through the mask and a second half of the target to be treated with a blanket treatment of ions unimpeded by the mask during a first time interval. The masking apparatus also includes a positioning mechanism to change a relative position of the mask and the target so that the second half of the target is treated with the selective treatment of ions and the first half of the target is treated with the blanket implant during a second time interval.
According to another aspect of the disclosure, an ion implanter is provided. The ion implanter includes a source of ions, a mask positioned upstream of a target positioned for treatment with the ions, the mask sized relative to the target to cause a first half of the target to be treated with a selective treatment of the ions through the mask and a second half of the target to be treated with a blanket treatment of the ions unimpeded by the mask during a first time interval, and a positioning mechanism to change relative positions of the mask and the target so that the second half of the target is treated with the selective treatment of ions and the first half of the target is treated with the blanket implant during a second time interval.
According to yet another aspect of the disclosure, a method is provided. The method includes positioning a mask a distance upstream of a target, treating a first half of the target with a selective treatment of ions through the mask and a second half of the target with a blanket treatment of ions unimpeded by the mask during a first time interval, changing a relative position of the mask and the target, and treating the second half of the target with the selective treatment of ions and the first half of the target with the blanket treatment of ions during a second time interval.
The present disclosure will now be described in more detail with reference to exemplary embodiments as shown in the accompanying drawings. While the present disclosure is described below with reference to exemplary embodiments, it should be understood that the present disclosure is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein, and with respect to which the present disclosure may be of significant utility.
For a better understanding of the present disclosure, reference is made to the accompanying drawings, in which like elements are referenced with like numerals, and in which:
The controller 112 can be or include a general-purpose computer or network of general-purpose computers that may be programmed to perform desired input/output functions. The controller 112 also includes communication devices, data storage devices, and software. The user interface system 114 may include devices such as touch screens, keyboards, user pointing devices, displays, printers, etc. to allow a user to input commands and/or data and/or to monitor the beam line ion implanter 100 via the controller. The controller 112 may receive signals from the user interface system 114 and/or one or more components or sensors of the beam line ion implanter 100. The controller 112 may control components of the beam line ion implanter 100 in response thereto.
The masking apparatus 120 includes a mask 106 positioned upstream of a target 108. The mask 106 and the target 108 may be positioned in a process chamber of the beam line ion implanter. One or more vacuum pumps and exhaust valves may establish a vacuum condition within the process chamber as known by those skilled in the art. The mask 106 may include a blocking portion 107 that blocks ions of the ion beam 109 from striking a front surface of the target 108. The blocking portion 107 may define one or more aperture 109 that allow portions of ions from the ion beam 109 to pass there through. Advantageously, the mask 106 is sized relative to the target 108 to cause a first half 108 a of the target 108 to be treated with a selective treatment of ions through the mask and a second half 108 b of the target to be treated with a blanket treatment of ions unimpeded by the mask 106 during a first time interval. As such, the mask 106 and other mask embodiments may be referred to herein as a “half mask.” The masking apparatus 120 may also include a positioning mechanism 118 to change a relative position of the mask 106 and the target 108 so that the second half 108 b of the target is treated with the selective treatment and the first half 108 a is treated with the blanket implant during a second time interval.
In one embodiment, the mask 106 may be fixed and the positioning mechanism 118 may include a rotating platen configured to support the target 108 and rotate the same 180° in between the first and second time interval while the mask 106 remains fixed to a portion of the rotating platen. In another embodiment, the target 108 may remain in a fixed position and the positioning mechanism 118 may include a retaining mechanism to support and rotate the mask 106. The retaining mechanism may include one or more fasteners to secure the mask and an actuator to rotate the mask 180° in between the first and second time interval while the target 108 remains in a fixed position. The positioning mechanism 118 may be controlled by the controller 112 and may provide positioning data to the same.
The plasma doping ion implanter 200 is illustrated as a stand alone system in
The plasma source 206 is configured to generate a plasma 240 in the process chamber 202. The plasma source 206 may be any plasma source known to those in the art such as an inductively coupled plasma (ICP) source, a capacitively coupled plasma (CCP) source, a microwave (MW) source, a glow-discharge (GD) source, a helicon source, or a combination thereof.
The bias source 290 provides a bias signal to platen 210 and the target 108 supported thereby. The bias source 290 may be a DC power supply to supply a DC bias signal or an RF power supply to supply an RF bias signal depending on the type of plasma source 206. In one embodiment, the DC bias signal is a pulsed DC bias signal with ON and OFF periods to accelerate ions 203 from the plasma 240 to the target 108 during the ON periods. Controlling the duty cycle and amplitude of such a pulsed DC bias signal can influence the dose and energy of the ions 203. The plasma doping apparatus may also include a controller 212 and a user interface system 214 of similar structure to those detailed with respect to
The mask 306 may be fabricated of graphite or another material that has a blocking portion 307 that sufficiently blocks ions 304. The mask 306 is illustrated as having four apertures 322, 324, 326, 328 for clarity of illustration. In one instance, the mask 306 may have many more apertures depending on the center to center spacing (X1) between apertures and the width (X2) of each aperture. In one embodiment, the mask 306 may have center to center spacing (X1) of about 2-3 millimeters (mm) and each aperture may be an elongated slot having a width (X2) of about 100-350 micrometers (μm) and a length of about 300 millimeters.
The target 308 may be one or more workpieces including, but not limited to, a semiconductor substrate, a solar cell, a polymer substrate, and a flat panel. The target 308 may include four separate solar cells labeled A, B, C, D in
Once the mask 306 and target are repositioned, a selective implant may now be performed on solar cells A and B while a blanket implant may be performed on solar cells C and D during a second time interval. As such, each solar cell A-D receives both a blanket and selective implant during successive time periods and the net result is that each solar cell A-D has a lightly doped region formed by the blanket implant and a more heavily doped region defined by the apertures 322, 324, 326, 328 of the mask 306. Whether the blanket implant is performed first (solar cells A and B) or last (solar cells C and D) the net result is the same. This is beneficial for many applications including when the solar cell is for use as a selective emitter solar cell. Furthermore, the target 308 and mask 306 may be positioned in the process chamber of the beam line implanter of
In operation of the selective emitter solar cell 500, photons 501 enter the solar cell 500 through the top surface 505. The photons 501 pass through an anti-reflective coating 510 designed to maximize the number of photons that penetrate the solar cell 500 and minimize those that are reflected away. The lightly doped region 530 may be an n-type region to form a p-n junction 520 between a p-type base 540 and the lightly doped n-type region 530. Those skilled in the art will recognize the p-type and n-type regions may be reversed. Photons with sufficient energy are able to free electrons from their atoms allowing them to flow through the solar cell and the front side contacts 526 to produce electricity.
The mask 706 may float on supports and keyed features and align to the platen 710 when rotated at 0° and 180°. The keyed features may directly couple and align the mask 706 to reference features on the platen 710. In this way, accurate, reliable, and time efficient alignment of the mask 706 to the target 608 may be accomplished.
Accordingly, there is provided a masking apparatus and ion implanter having the same. The ion implanter having the masking apparatus is able to provide a two step chained ion treatment sequence for a target. A first half of the target receives a selective treatment of ions through the mask with the other half receives a blanket implant during a first time interval. Then the relative position of the mask and target is changed so opposite halves of the target are now treated with a selective and blanket implant. Hence, process time for performing chained implants is reduced to improve the throughput performance of the ion implanter. In addition, precise alignment of the mask to the target is promoted to result in better device performance for devices being formed on the target.
The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure is as described herein.
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|U.S. Classification||250/492.21, 438/510, 257/E21.042, 250/492.3, 250/492.2, 257/E21.043|
|International Classification||A61N5/00, H01J37/317, H01J1/54|
|Cooperative Classification||H01J2237/20214, H01L21/266, H01J37/32412, H01J2237/31711, H01J37/3171, H01J2237/024|
|European Classification||H01J37/317A, H01L21/266, H01J37/32M24|
|May 7, 2010||AS||Assignment|
Owner name: VARIAN SEMICONDUCTOR EQUIPMENT ASSOCIATES, INC., M
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CARLSON, CHARLES T.;WEAVER, WILLIAM T.;SIGNING DATES FROM 20100506 TO 20100507;REEL/FRAME:024353/0343
|Jun 24, 2015||FPAY||Fee payment|
Year of fee payment: 4